Subj : Commodore Pet keyboard re
To   : James Harris
From : Ed Vance
Date : Wed Jan 10 2018 22:14:00

01-10-18 17:17 James Harris wrote to All about Commodore Pet keyboard re
Howdy! James,

I was wondering if the Keyboard Switches are called "Cherry Switches"?

A Cherry Switch (as I remember them being called) is a (almost) 3/4 Inch
Plastic Box with two contacts on the bottom.

I built a Netronics ASCII Keyboard kit and after I finished one of the
Keys didn't do anything when I pressed it.

A friend used a knife to cut the bottom plastic piece from the rest of
the Switch.

I can't remember what He did (probably bent the contacts a little bit),
and then glued the bottom part with plastic glue from a tube and then
soldered the assembled Switch back on the PC Board, put the Key Cap on
it and the Switch worked when pressed.

Hope this idea is of help.

If a NEW Cherry Switch is what You need they may still be available at
Digi-Key or JamesCo or other Parts Stores.


 JH> @MSGID: <5A5689A0.2429.cbm@capitolcityonline.net>
 JH> To my surprise, I find I have a Pet which works - all apart from the
 JH> keyboard, that is. So I have a query about fixing it.

 JH> So far, I have removed the keyboard and found that the PCB contacts
 JH> work if shorted with something conductive. Therefore the problem is
 JH> with the little black pads that a keystroke presses against the PCB. I
 JH> have tried these things:

 JH> * cleaning with isopropyl alcohol
 JH> * cleaning with contact cleaner
 JH> * abrading with a pen eraser

 JH> The latter was not really effective as there is too much give in the
 JH> part of the key which supports the pad so I would say that the
 JH> operation failed to abrade the pad successfully.

 JH> Where I am now is that a few pads work but most do not. I have tried
 JH> putting two meter test prods on the pads to measure resistance and
 JH> found that some only become conducive with significant pressure. I
 JH> guess that the rubber of some of them has become too hard with age.

 JH> So what can I do to fix them? Any ideas?


 JH> One idea I've had so far is to apply some conductive matter to the
 JH> pads. I have tried a product called Keypad Fix on a remote but found it
 JH> dries to be too inflexible and crumbles on use, albeit that that was on
 JH> larger contacts.

 JH> Another option is conductive paint such as

 JH> https://uk.rs-online.com/web/p/solder-pastes/8352699/

 JH> A further option is to cut tiny copper-film discs and stick them to the
 JH> existing pads.

 JH> Any of those good options? Other suggestions welcome.


 JH> --
 JH> James Harris

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